1. Field of the Invention
The present invention relates to an automatic focusing apparatus used in, e.g., a camera and, more particularly, to an automatic focusing apparatus for performing a predicted AF (auto-focus) operation and a focusing operation of an object, which is moving in a direction perpendicular to an optical axis.
2. Description of the Related Art
Conventionally, a large number of apparatuses for detecting and processing movement of an object in an automatic focusing apparatus for a camera have been proposed. For example, in Published Unexamined Japanese Patent Application No. 60-166910, a difference between object image signals before and after an elapse of a predetermined period of time is calculated to detect movement of an object image, and a camera-shake alarm is generated to predict that a focusing operation cannot be performed. In, e.g., Published Unexamined Japanese Patent Application No. 60-214325 discloses a means for detecting movement of an object in the optical axis direction on the basis of a change in defocus amount to predict the position of the object after an elapse of a predetermined period of time, and correcting the lens driving amount.
In an apparatus disclosed in Published Unexamined Japanese Patent Application No. 60-166910, when the movement of an object is detected, a photographer determines that a focused photograph cannot be obtained, and he or she misses a photographing chance. Even when the photographer performs a photographing operation, a focused photograph cannot be obtained.
In an apparatus disclosed in Published Unexamined Japanese Patent Application No. 60-214325, since movement of an object in the optical axis direction is detected, and a lens follows the detected movement, an object that is moving straight along the optical axis direction can be focused. However, in the following case, a focusing operation cannot be performed.
More specifically, in this apparatus, since only a change in defocus amount is detected, when an object 1 is moving in a lateral direction (in a direction of an arrow G.sub.1 in FIG. 1A) perpendicular to the optical axis of a camera 2, as shown in FIG. 1A, an object image falls outside a distance-measurement frame for detecting a defocus amount. For this reason, a wrong moving speed is detected. When objects 1 and 1' are present side by side at two close distances, as shown in FIG. 1B, if a photographer slightly changes an angle of the camera (in a direction of an arrow G.sub.2 in FIG. 1B), an object to be subjected to distance measurement is changed. For this reason, the defocus amount changes inadvertently.
Due to a change in defocus amount, the camera determines that the object is moving, and corrects the lens driving amount. For this reason, a focused photograph cannot be obtained. More specifically, the camera merely detects only a change in defocus amount, but does not detect whether or not an object to be subjected to distance measurement is a single object.